# The Naked Scientists Forum

### Author Topic: What happens when light slows down?  (Read 2610 times)

#### Dlarah

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• Posts: 9
##### What happens when light slows down?
« on: 14/10/2008 21:22:45 »
When light travels in vacum the speed is C, albeit when it travles in the atmosphere it is slowed down, right?

If then light travles through an aquarium in space, it will slow down, but when it enters space again will it move at C or at the slowed speed?

If the light stays slowed down, you would be able to decrease the speed of light until you can move faster than the lightwave, right? If so what would happen?(my physics teacher said that if you were to move faster than light you would travel in time)
« Last Edit: 18/10/2008 20:58:27 by chris »

#### syhprum

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##### Re: What happens when light slows down?
« Reply #1 on: 14/10/2008 21:39:25 »
It is certainly possible for particles to travel through air or water at faster than the speed of light in the medium, and Cherenkov radiation is produced
See this URL for a detailed account http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html
« Last Edit: 14/10/2008 21:42:22 by syhprum »

#### Soul Surfer

• Neilep Level Member
• Posts: 3345
• keep banging the rocks together
##### Re: What happens when light slows down?
« Reply #2 on: 14/10/2008 23:15:51 »
Light is not like a truck which once slowed down needs an input of energy to speed it up

The light in effect is always travelling at the speed of light but when it enters the liquid or the clear solid the presence of a large number of densely packed atoms effectively makes its path altough on average straight a bit wiggly because of the presence of the electromagnetic fields in the atoms so on average the light appears to slow down a bit.  However the moment the light exits the material it is free to move in a straight line again and so on average it returns to the normal speed of light.
« Last Edit: 14/10/2008 23:17:37 by Soul Surfer »

#### The Naked Scientists Forum

##### Re: What happens when light slows down?
« Reply #2 on: 14/10/2008 23:15:51 »